1. Field of the Invention
The present invention relates to a D/A converter (digital/analog converter or DAC). In particular, the invention relates to an audio signal processing circuit having the D/A converter and a liquid crystal display device including the same.
2. Description of the Related Art
In recent years, liquid crystal flat panel displays capable of displaying an image clearly have been widely used and employed as displays for mobile apparatuses such as a mobile phone, a digital camera, a notebook computer, and a PDA (Personal Data Assistant).
Such a semiconductor device having a display function, in many cases, requires an audio circuit for outputting sound in addition to a display portion. Therefore, in conventional display devices, an audio signal processing circuit is generally provided as a dedicated LSI.
As the digital audio technology advances, storage of sound and communication mediums have been more digitalized, and thus a D/A converter for converting digital data into analog data is essential for such mobile apparatuses. As the D/A converter, there is known a D/A converter as shown in FIG. 3 of Patent Document 1, in which an upper limit reference voltage VH and a lower limit reference voltage VL are divided by the capacitance ratio and a divide ratio thereof is changed by changing a combination of capacitors by a switch based on an input digital signal, and a D/A converter as shown in FIG. 1 of Patent Document 2 (referred to as a resistor string D/A converter), in which an upper limit reference voltage VH and a lower limit reference voltage VL are divided by a plurality of resistors connected in series therebetween and a divided potential is outputted by selecting one of connections between the resistors based on an input digital signal by a switch.
[Patent Document 1] Japanese Patent Laid-Open No. 2000-341125
[Patent Document 2] Japanese Patent Laid-Open No. 09-83369